Digital video systems generally include image capturing components which create a digital video signal for a desired scene and signal processing components which perform various format conversions or other processing tasks to ultimately produce an input to a digital video display monitor which displays a video image of the desired scene.
Digital video signals are typically made up of a stream of data defining a series of image frames which may by displayed at a video monitor rapidly in succession at a desired frame rate to produce a video image. Each image frame (hereinafter referred to simply as a “frame”) is made up of a number of pixels with each pixel defining the light intensity at a particular point in the frame. Each pixel in a frame is defined by pixel data which specifies the light intensity in terms of a digital value or set of digital values in the case of color video. For example, each pixel in a digital video frame may be represented by three 8-bit values each defining a respective color component for the pixel, such as red, green, and blue. In addition to the color component data, the pixel data may include additional data defining other characteristics of the point in the frame such as transparency for example.
In some cases the digital video signal generated by the image capturing components of a digital video system may be at a lower frame rate than the frame rate at which the video display monitor operates. For example, a medical video imaging system may employ a light sensor array that detects light over a relatively long period of time (that is, a long integration period) to generate a respective frame and thus may create frames at a slower frame rate than the frame rate at which frames are to be displayed by the system display monitor. Such a situation may occur with cameras operating in fluorescence imaging modes where the image capture system is light starved and therefore forced to employ a long integration period for each frame.
Frame replication is a common solution to address the situation in which a given digital video signal at a first frame rate must be used to drive a video display monitor at a higher frame rate. Frame replication may be accomplished by buffering the frames of the lower frame rate video signal in buffer memory so that the frames may be read at a higher rate to produce the desired higher frame rate signal. In this solution, each frame of the lower frame rate video signal is replicated as many times as necessary to produce a video signal at the desired higher frame rate. Take, for example, the case where a given set of image capturing components generate a digital video signal at 15 frames per second (“fps”) while the video signal is to be displayed on a display monitor which operates at an update/refresh rate of 60 fps. In this case, each frame of the lower frame rate digital video signal may be buffered in suitable buffer memory, having a suitable buffer memory architecture such as a classical triple buffer architecture for example, and read four times from that memory to produce a digital video signal having the desired 60 fps rate. That is, each frame of the lower frame rate digital video signal is replicated four times and each replicated frame is placed in an output digital video signal having the higher frame rate. In this frame replicating technique, the digital video signal ultimately sent to the display monitor causes the display monitor to show the exact same frame (exact down to each respective pixel in the frame) four times before the next frame from the lower frame rate digital video signal can be displayed on the display monitor.